The invention relates to a conveyor belt for the transport of workpieces, in particular for the suspended transport of platelike workpieces, such as metal sheets or boards, with a belt body having suction orifices which are connected to a vacuum duct in a vacuum device, the conveyor belt, together with the workpieces to be laid onto it, being guided, in bearing contact, past the vacuum device in the transport (plane) direction, and the workpieces being retained on the conveyor belt by generating a vacuum in the vacuum duct and consequently at the suction orifices, and with two or more rear sealing lips integrally formed on the belt body, the two sealing lips engaging into at least one sealing gap in the vacuum device for the purpose of sealing off the vacuum duct. In addition to suspended transport, of course, horizontal and even vertical transport are also possible.
A conveyor belt of the initially described form of construction became known from DE 196 14 741 C1. This conveyor belt is used in conjunction with a combined vacuum/magnet system. It consequently serves for the transport of both ferromagnetic workpieces (by means of a magnet system) and nonferromagnetic workpieces (by means of the vacuum system). This combined operating mode normally means that compromises are made in the design of the known conveyor belt. These may include a reduced suction capacity which is attributable to the use of flat seals. Also, leakages cannot be ruled out in the known conveyor belt. In addition, bent or dented metal sheets or boards are not always sufficiently retained. This is because the front suction recesses are scarcely in a position to be able to adapt to the contour of a workpiece having pronounced curvature.
Irrespective of this, DE-A-30 01 531 discloses a conveyor belt with textile or metallic reinforcements embedded into a core layer made of rubber or elastomeric plastics. In addition, elevations, which serve partly as suction recesses, are located on a cover plate. The problems involved in the elimination of leakages and in suction adapted to the workpiece contour are not discussed.
Finally, DE-A 41 02 130 discloses a two-lip seal, in which, while sealing remains the same without any change, the distance between radial and axial annular faces and the sealing lips is greater than 0, equal to 0 or smaller than 0, with composite systems of these being included. In this way, various sealing conditions (sliding seal, labyrinth seal or composite systems of these) are to be capable of being controlled in the case of a two-lip seal with the aid of the simplest means.
The object on which the invention is based is to develop a generic conveyor belt in such a way that leakages are minimized and, at the same time, optimal adaptation of the conveyor belt to the workpiece contour becomes possible.